Method of recovering hematoxylin



Feb. 13, `1945 R. L. DREW METHOD OF RECOVERING HAEMATOXYLIN Filed Jan. 19, 1943 W ma. mm

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ATTORNEYS Patented Feb. 13, 1945 UNITED Y American Dyewood Company, NewYork, N. Y.,

`a corporation of Pennsylvania v 9,1943,lseria.i-No. 472.8159V y y comms. tclgzeofsss) Application January This invention relates to the recovery of hematoxylin from aqueous extracts of logwood. and particularly to an improved'method of effectively separating constituents of such extracts which prevent crystallization of` the4 hematoxylin.

` Logwood is extractedlby chipping and digest-` ing the -chips with Water and steam. The extract contains in addition to hematoxylin other Water soluble constituents, including glucosides,which act as dispersing `agents to peptize the solution,

thereby preventing crystallization of the hematoxylin. The recovery oi hematoxylin crystals from logWood extracts `has been heretofore `a tedious and costly operation conducted only on a laboratory scale to produce relatively insignicant quantities `of thecrystals for use `in stains ing slides for mircoscopic Work. m l.

It is the object of the present invention to provide a simple and effective method of recover- 'ing hematoxylin crystals at relatively slight cost and in a manner adapted for commercially practicable operations.

Another object of the inventionis the removal from the logwood extract of water'sluble constituents .acting as dispersing` agents therein to,

prevent crystallization ofhernatoxylin present in the extract'l l Y Other objects and advantages of theinvention will be apparent as it is bettervunderstood by reference to the following specication and the accompanying drawing, diagrammatically illustrating anapparatus suitable `for the practice of the invention. l l

I have discovered that the effect of glucosides or other Water soluble dispersing` agents in log-` wood extract canbe overcome by `suitably adjusting the pH and temperature of theextract to eiect a complete or partial iiocculation of the dispersing agents in the extract. `When the effect of the disbursing agents is thus reduced or removed, the hematoxylin may be crystallized readily by seeding with hematoxylin crystals and cooling the solution. Agitation isdesirable during coolf ing toensure theproductionof smaller and purer crystals. The resulting crystals and the floc'may beseparated from the mother liquo-r byA ltration. The mother liquor may then be discarded. To facilitate filtration, itmay be `desirable sometimes, although it is not essential, to add an` agent such as FiltereCel or some filter aid. t

The filter cake including `the hematoxylin crystals and the i'loc is then treated with Water to re-dissolve the hematoxylin, leaving the floc which can be separated by filtration. The liquor containing the dissolved hematoxylin is then rer. soon as the crystallization is com crystallized and the crystals recovered by filtration. Further solutionand rfc-crystallization will l improve the purity of the crystals. m

The logwoodv extract is preieraoly in fairly concentrated form, that is about 40 Tw., and is heated prerera'olytoa temperature of Bo to illu C.V 'lheextr'act 1s aciqii'led preferably with hydrochloric acid, though other acids such as sulphuric l acid may be used, to a pH in the neighborhood o1" 1.o. The temperature ismaintainedl for a brief period, for example aboutone-halr hour or until nocculation of the dispersing agent in the solution is substantially effected.

n lmhe conditionsV or operation may be varied. With an extract at about-lflw., the preferred pHv would ,be labout `1.3. With theextract at 45 Tw., a `pH of: 2 lwould be satisfactory. Usually,

"however,` it is not `desirableto work with the exl tract at `higher than 40` Tw., because of mechanical difficulties in stirring. When occulation is effected, the extract is seeded with crystals of hematoxylin andcooled fairly rapidly to about 20 l C lpreierably with agitation. Crystallization can be completed Without agitation, but the crystals will be larger and less pure. i

pleted, the mixture of mother liquor, crystals Vand floc is iiltered.` The liquor may be deliveredlto Waste.

The iilter cake is then treated with water, pref,` erably with` agitation and heating `to dissolve the l hematoxylin, thus leaving the oc in suspension. A secondliltrationremoves.the floc which may bedisposed of as Waste. The solution is seeded with crystals of hematoxylinand `cooled rapidly to about 20 C.l to recrystallize `the hematoxylin.

The crystals are removed by ltration. The liquor can be returned to dissolve the hematoxylin in the lter cake from` the initial operation.

While `I prefer to use an apparatus as dia` grammatically illustrated in the accompanying drawing, the details are not essential. In place of aplurality of receptacles, `each provided with stirring means, the operation may be conducted in a single receptacle to which the material is returned for each successive step. An ordinary `filter'pressmay be employed to separate solids fromliquids in the severaloperations, but other well-known devices are equally `useful for` that purpose. l y

Referring to `the drawing, `5 indicates a receptacle having a jacket B to which steam or cooling water may be introduced through a pipe 1, escaping through a pipe `8. Any suitable heating and cooling agentmay be employed in the successive steps of` the operation. An agitator 9 is mounted on a shaft IU and driven from any suitable source of power such as a motor II. In the receptacle 5, the logwood extract is, as previously described, first lheated to the desired temperature and acidified to the proper pH. As the result of acidification, the dispersing agent in the extract becomes flocculated. stirring by means of fthe `'agitator 9 is utilized ,preferably after theiextract has :been seeded withhematoxvylin crystals and during the period while it is being cooled to eiect crystallization of the hemf l atoxylin. When crystallization is completed, ya valve I2 is opened and the mass yis delivered to a lter press I3. The mother liquor `escapes through a pipe I4 while the ffloc fand/crystallized hematoxylin is retained bythe press. The "filter cake is withdrawn and delivered to .a .second receptacle I5 having a jacket I6 supplied with steam or other heating agent through a lfp'ipel`'l. The heating agent escapes through a pipe I8. An` agitator I9 is supported on a .shaft 20 and adapted to be driven v"from asuitable source of power such as a motor A2|. Water, or prfera-bly liquor from a subsequent operation, is introduced through 'a'pipe 22 to dissolve'thehematoxylin crystals inthe receptacle I5,'1eavin'gth'e oc in suspension. A valve v23 -is then nopened to deliver 'the material toma'ltenpress 2:4"Which separates the floc from 'the liquor escaping through a 'pipe 25. The' iilter'cake, consisting 'of the'floc, maybe discarded.

The pipe 25 delivers thesolution 'containing the dissolved hematoxylinto'a*receptacle 26 hav---` ing a jacket l21 adapted 'to be supplied rwith'coolingcwater through a pipe 28. The'waterescapes through a pipe 29. agitator 3'0'is supported on a shaft 3| and'adapte'dto'be driven Vfroma'ny suitable source of power such as a motor 32. 'In the receptacle v2-3 the'solution 'of hematoxylin is seeded with hematoxylin crystals fand is cooled preferably with agitation. Whencrystallization is complete,'a valve 33 is `opened'to deliver fthe material lto a lter press 34 where the crystals are -separated from Athe liquor. The liquor isfdelivered to a pipe-135 and `pump 36 which returns it through the pipe22-to-thelreceptacle115. r`Solution of the hematox-ylin 'crystals-and re-crystallization thereof will improve 'the '-purity of '-th'e crystals. v l

The procedure'as hereinbefore described avoids the complicated laboratory -methods which were heretofore' the procedures followed lin fsecuring hematoxylin crystals. As hereinbeforegindicated,- while apparatus such as that illustrated -lis preferable for largescale operations, allof the necessary steps can be carried on .in the freceptacle 5 and the filter press .I3 .or soxneequivalent separating device. By following the procedure described, hematoxylin crystals I'can ber recovered cheaply and eiiectively from logwood Vextract.

Various changes may .be'made in the procedure and apparatus without` departingfromflthe invention or sacricing lthe advantages thereof.

I claim:

1. The method.y of recovering 'hematoxylini'from aqueous logwood extract which comprises acidifying the extract `to 'occulate fthe Vdispersing agents therein,-crystallizingthe hematoxylin, separating the loc and the crystasl from the'mother liuqor, re-dissolvingv the hematoxylin crystals fin water, and separating the floc from the solution.

2. The method of recovering hematoxylin from aqueous logwood extract which comprises'acidifying the extract to flocculate the dispersing agents therein, crystallizing the hematoxylin, sep-` arating the iioc and the crystals from the mother liquor, re-dissolving the hematoxylin crystals in watenwseparating the A'lloc from the solution, and reecrys'tallizing the fhematoxylin from the solution.

l'3. The method of recovering hematoxylin from :aqueous logwoodtextract which comprises hel inthe extract and adjusting the pH to approxi v anatelylbetween .-1.3 l.and 2, thereby iiocculating the Iiiispersing agents therein, crystalllzing the i "hematoxylinfseparating the oc and the crystals lfrom .the mother liquor, re-dissolving the hema- `toxylin crystals in water, and separating the iioc from the solution.

4. .The method .of .recovering hematoxylin from aqueous logwood extract which `comprises 'heating Vthe extract .to'approximatly 95 to 100 C. and adjusting 'thepH to approximately'between f1.3 and "2, thereby ilocculating `the dispersing agents'therein, crystallizingthehematoxylin, separating thefloc andthe crystals from the mother liquor, 41re-.dissolving 'the hematoxylin Acrystals in water, and separating the "locfrom the solution '5. The method of recoveringheniatoxylin Ifrom f aqueous logwood extract which -compri'ses'heatingthe'extract and adjustingth'epH to approxim'ately between '1.3' and "2 thereby iioccu'lating j thev dispersing `agents -therein, crystallizing the nematoxyhm'separating `thai-loc and the crystals from V4the mother liquor, re-dissolving the hematoxylin 'crystals"in"water, and separating the'floc from the solution. l

6. "The method 'of vrecoveringhematoxylin from aqueous logwoofd A'extract 'which comprises jheating 'the extractjand 'adjusting "the "pH yto Iapproximately between I1.3 Yand 2 lthereby iiocculating the dispersihg agents therein, rcrystalliziing the hematoxylin, `separating `the loc and lthe crysf tais from fthe `mother '-li'quor, jrer-dissolving the 'hematoxylincrystals'in' watenseparating the v'iioe fromthessolution"andrecrystallizing the hematoxylin from the solution.

7. "Them'etho'dfoi'"recovering hematoxylin -from aqueous vlogwoo'd Jextract which comprises heating the-extract to "approximately to "10U" C., and adjusting `the pH tto approximately "between l1.3. and 2 "thereby `:ilocculating the `dispersin'g agents therein, crystallizing the hematoxylimseparatin-g-'the flocan'd 'the crystalsifrom-the'mother l liquor, re-dissolvingthehematoxylin crystals in Water, separating fthe ffloc 'from l-the "solution, and rel-crystallizing fthe hema-toxylin `rfrom :the solution. l

18. 'Thetmethod of recovering "hematoxylinf from aqueous llo'gwood `.extract lwhich `:comprises 'hea'ting V:the extract and y.adjusting Ithe fpH 'lto approximate'ly between i123 "and21with'hydrochloric acid ther'ebyi iiocculating fthedispersing agents i therein, crystallizing the hematoxylin, separating the floc :and the crystals from l.the m'otherliquor, redissolving the l:hem'atoxylincrystals in' water; separating the .floc :from :the :.solution, i and =.re-crystallizing :thezhematoxylin from 1 the solution.

:RAYMOND L. r`DREW.

CERTIFICATE oE CORRECTION. Patent No. 2,569,5LL5. February 15, 19u51.

RAXTIOND L. DREW.

It is hereby certified that error appears in the printed specification of the'above numbered patent requiring correction as follows: Page l., second column, line h, beginning with "The logwood extract" strike out all to `and including the 'word and period "effected," in line l5, and insert instead the following --The logwood extract is preferably in fairly concentrated form, that is about MOO Tw., and is heated preferably to a ten-lperature of 95o to 1000 C, The extract is acidified preferably with hydrochloric acid', though other acids such as sulphurio acid may be used, to a pH in the neighborhood of 1.8. The temperature is maintained for a brief period, for example about one-half hour or until flocculation of the dispersing agent in the solution is substantially effected.;

and that the said Letters Patent should be read'wi th this correction therein that the same may conform to the. record of the case in the Patent Office.

Signed and sealed this l5th day of June, A. D. l9lp5.

Leslie AFrazer* (Seal) Acting Commissioner of Patents.` 

